Three interlinked approaches are planned: (1) The development and regeneration of sensory appendages, the abdominal cerci of the house cricket Acheta domesticus will be further analyzed by anatomical, electrophysiological and ultrastructural methods to determine the "rules" for neural circuit assembly, with special attention to emerging concepts of pattern formation, and with relevance to vertebrate studies. (2) Embryogenesis of cercal sensory projections and recipient neuropile will be characterized by light and electronmicroscopy in normal and laser ablated material. (3) Sensory projections in homeotic mutants of Drosophila melanogaster will be mapped by means of cobalt filling in order to determine the behavior of neurons where there is a mismatch between center and periphery.